The present invention relates to solvent-activated and solvent-sensitive color forming compositions, their method of making and method of use.
Prolonged exposure to, or immersion in, certain solvents (e.g., water) can adversely affect the physical, chemical and mechanical properties of some polymer materials, composite materials, and synthetic construction materials. For example, the exterior of golf balls typically consists of one or more polymer materials. A golf ball that has been submerged in a water hazard for an extended period of time will exhibit inferior flight characteristics compared to a new golf ball, despite the superficial similarity in appearance of the two golf balls (Golf Digest, September 1996). In some instances, the diminished performance of certain materials caused by prolonged exposure to a solvent is temporary and mostly reversible if the solvent is removed by drying the affected materials. In other situations the effects are permanent and performance is irreversibly damaged. In certain situations, any exposure to a solvent, however brief, may create performance concerns. Thus, there is a need for a color-based indicator that can be incorporated into various solvent-sensitive materials which will alert the user to the possibility that the performance of the materials has been compromised by exposure to, or immersion in, a given solvent. Ideally, color formation would be either reversible or permanent based on different formulations of the indicator and the material it is combined with.
Several water-sensitive color systems currently exist. U.S. Pat. No. 5,130,290 to Tanimoto discloses a water-sensitive coloring sheet which includes a substrate and a water-sensitive coloring layer containing an unencapsulated color developing material that reacts with a dye when the coloring layer is wetted. The inclusion of a desensitizing material in this system results in a reversible color formation system (i.e., the removal of water results in the removal of the color). U.S. Pat. No. 5,501,945 to Kanakkanatt discloses the concept of a reversible system in which water sensitive chemichromic dyes are incorporated into polymers used for various packaging applications. U.S. Pat. Nos. 5,823,891 and 5,938,544, both to Winskowicz disclose a color-forming system for use with golf balls which utilizes a water permeable covering over the core of a golf ball, and a water soluble pelletized or microencapsulated colored dye near or within the covering.
All of the discussed systems require some type of colored dye which when subjected to the correct stimulus undergoes a color change. Such dyes must often be processed, i.e., pelletized or microencapsulted, before they can be incorporated into a particular material. Processing dyes in the manner adds difficulty and expense to the process of creating a water-activated color forming material. Furthermore, these dyes may be removed by simply bleaching the colored material.
These, and other deficiencies of the prior art are overcome by the present invention which provides a color-forming composition that includes a solvent absorbing material such as a polymer, a chelating agent or xe2x80x9ccolor formerxe2x80x9d that is compounded with the solvent absorbing material, and source of metal ions such as zinc acetate. The metal ions form a chelate complex with the color former as a solvent (e.g., water) is absorbed by the polymer resulting in the polymer changing color. The color-forming composition of the present invention is white or colorless after initial processing and does not change color until it has absorbed the solvent. This color-forming composition is essentially xe2x80x9caquachromicxe2x80x9d meaning that color change occurs upon exposure to liquid water, but is not xe2x80x9chydrochromicxe2x80x9d because exposure to moderate humidity alone does not initiate a color change. Once the color change has occurred, the color-forming composition of this invention is unaffected by treatment with typical solutions designed for color removal for extended periods of time.
Therefore, it is an object of the present invention to provide a color-forming composition that can be used for multiple purposes, including use as the outer cover of golf balls, whereby prolonged exposure of the color-forming composition to a liquid solvent, such as water, results in a detectable color change of the composition.
It is an additional object of the present invention to provide both a reversible and an irreversible color forming composition, whereby the color change is permanent upon the removal of a solvent from the composition, or whereby the color change is temporary, and the color fades from the composition upon removal of the solvent from the composition, but can be regenerated upon repeated exposure to the solvent.
Further objects, advantages, and novel aspects of this invention will become apparent from a consideration of the figures and subsequent detailed description.